Some of my ferals seem to keep drones more than the Italains. I see a few all winter, but not very many. Most were killed back in October or before. Sometimes a queenless hive will keep more drones too. Usually the Italians seem to kill them all off in the early fall.

Keeping drones in queenless colonies (until mature) is a technique used by many artificial inseminators. You can get drone comb laid up in the hive you wish to breed from and then remove the frame and raise it in a queenless hive (with plenty of young workers).

They rarely throw them out. If there is no chance of a hive being able to raise a queen the only way they can get their genes through to the next generation is through drones laid by themselves (this is why we get laying workers).

We can utilise this survival technique as a method for keeping drones. They seem to treat any drone brood added the same way as their own providing the colony has been queenless for some time. You can keep these units going for ages by adding sealed brood weekly.

In Australia where the Winters are relatively mild they easily hold drones all winter this way (of cause feeding the hive syrup through the dearth peroids.